Maracaibo Basin in Western Venezuela, Figure 1, has an area of 90,000 square kilometers. It is isolated from the rest of Venezuela on the East and South, and from Columbia on the West, by mountain ranges which reach a height of 5,000 meters at the southern boundary of the Basin. Lake Maracaibo and its marginal swamps cover 17,700 square kilometers of the Basin. The Lake proper, approximately 150 kilometers long by 110 kilometers wide, is connected to the Gulf of Venezuela by the Straits of Maracaibo and broad shallow Tablazo Bay. It is about 50 kilometers from the lake proper to the gulf. Tablazo Bay is separated from the Gulf of Venezuela by a series of shifting sand islands and bars.